Rory McIlroy insists he still has the game that won him two major championships and saw him rise to world No. 1.

The Northern Irishman has been hit with plenty of off-course distractions in the past few months, including a heavily-criticised switch of club manufacturer and a split from management company Horizon Sports, as well as a high-profile relationship with tennis star Caroline Wozniacki.

The 24-year-old admits he has been left frustrated by his winless start to 2013, having surged to the top of the rankings last year after four victories in the US, before going on to win a second major at the US PGA Championship and topping the money lists on both sides of the Atlantic.

"Of course you want to come into this year and try and do the same sort of things," McIlroy said. "It just hasn't really happened. I haven't lived up to my own expectations this year, but I'm working hard to try to live up to them, working hard to try and get the game back to where I know it can be."

McIlroy's poor round at the Memorial featured just two birdies, offset by six bogeys and a costly double at the par-3 12th where he four-putted from 40-feet.

When asked if there was any relation between his erratic form and what had been happening to him outside the ropes, he simply replied: "No."

He added: "Once I'm [at a tournament] I'm focused on what I need to do. Right at the moment it's not happening for me. I don't think I've played as bad as this score suggests. It was just one of those rounds that sort of got away from me.

"I'm pretty frustrated. I'm trying not to let it get to me. It is what it is and a few bad rounds of golf isn't going to ruin anything, but I'd definitely like to start playing [better]."

Reflecting on recent weeks, where he has recorded top-ten finishes at the Wells Fargo Championship and Players Championship before crashing out at the halfway stage of the BMW PGA Championship last time out, McIlroy added: "I felt like it was really coming around at Charlotte and TPC, I started playing some good golf.

"And last week, Wentworth was bad conditions and stuff. It was sort of a weird week. I don't really have many explanations for this. I felt like my game was good. I felt like I was coming in here and hitting the ball well. I felt like I needed to hole some more putts and things would be okay.

"I'm still sort of struggling on the greens a bit, and I just missed a few too many shots out to the right and that cost me. That's sort of been my big miss all of this year."